Method of operating a tow machine



April 18, 1961 H. J. M DERMOTT METHOD OF OPERATING A TOW MACHINE Filed July 7, 1959 MACHINE IN OPERATION LOWER COAGULATING BATH STOP FLOW I OF SPINNING SOLUTION RINSE SPINNERETS COLD WATER WITH COAT SPINNERET FACES WITH OIL RESTORE COAGULATING BATH TO OPERATING LEVEL START FLOW OF SPINNING SOLUTION U tsdfifim e 2,980,493 7 METHOD OF OPERATING A TOW MACHINE Henry I. McDermott, Collingdale, Pa., assignor to American Viscose Corporation, Philadelphia, Pa., a corporation of Delaware Filed July 7, 1959, Ser. No. 825,464

Y 3 Claims. (Cl. 1s s4 This inventionrelates to the production of'tow, particularly a tow of artificial wet-spun filaments. More methods difier primarily in detail, basically the process involves the extrusion of viscose through a spinneret into an acid coagulating bath, stretching the newly coagulated filaments, usually between a pair of godets, applying various after-treating liquids to the filaments and col- 1 lecting them into a package. Each spinneret normally contains only enough holes or orifices to form the number of filaments desired for a sin'gle'yarn strand. In a well-known type of machine, a large number of spinnerets are individually mounted in an elongated trough containing the coagulating or spin bath. ,The filaments emerging from the spinnerets are led in individual yarn forming bundles to separate godets and from the godets the separate bundles are led either into troughs where the after-treatment liquids are applied or to separate thread-storage, thread-advancing reels where the aftertreatment liquids are applied. Thus in yarn production, the various treatments are usually performed on individual yarn forming bundles of filaments. When one bundle of filaments breaks or an individual godet or threadadvancing reel ceases to function properly, the spinneret which is the source of that bundle is removed from the spin bath and permitted to flush into a waste removal container during the time necessary to repair the broken or malfunctioning element. The spinnerets are mounted upon individual, swingably mounted rounders to permit their removal from the bath. The reason the viscose is allowed to continue to flow and be wasted is that the nature of viscose is such that if the flow is shut off there is great difiiculty in later restarting it and the total amount of material extruded through a single spinneret during a relatively short period necessary to correct the undesirable condition is not economically significant.

For certain purposes, so-called spun yarn, that is, yarn formed by twisting together staple fibers or relatively short length filaments, is superior to continuous filament yarn, When the staple fiber is viscose rayon or other man-made fiber,'the fibers are generally formed as continuous filaments, a number of which are gathered into a tow and then cut, broken or otherwise severed into desired fiber lengths. Machines for spinning tow differ from machines for spinning yarn in several respects For one thing the individual spinnerets normally contain a much larger number of orifices since all filaments issuing from a spinneret are not destined to form a yarn and for another, the filaments issuing from all spinnerets are brought together to form the tow as quickly as possible whereby many of the liquid aftertreatments and sometimes the stretching may be performed on the tow itself rather than on the individual bundles of filaments. For another thing the tow of a Patented Apr. 18, 1961 "ice.

tow machine is much larger than the tows formed on yarn spinning machines. The cutting of the continuous filaments into staple is facilitated when the cutting is performed onthe large tow rather than on the smaller bundles. Tow or staple machines are notable for extremely large production as'compared with yarn spinning machines.

Recently a tow machine has been developed wherein a very large number of spinnerets each of which has a large number of filament-forming orifices are mounted in a single coupling. One example of such a coupling is described in applicants co-pending application Serial -No. 726,098, filed April 3, 1958. With this arrangement the bundles of filaments issuing from the individual spin nerets are brought to'gether very quickly, either before emerging from the spin bath or immediately thereafter, to form the tow. This assures uniform treatment of all filaments because the stretching and after-treatments are performed on the tow itself and each filament can be made to have substantially the same length of travel all the way from the spinneret to the cutting station.

This invention finds its greatest utility in connection with a tow machine and particularly with a tow machine wherein a large number of spinnerets are mounted in a single coupling. While such machines are intended for continuous operation, it nevertheless becomes desirable from time to time to stop the machine for limited periods of time which may be from one to three hoursmore or less. These stoppages may be necessitated-by the need for adjusting the cutter or for maintenance of the godets or for a number of other reasons. Since a single coupling containing many spinnerets necessarily has substam tial weight and size, special arrangements would have to be made if the coupling were to be removed from the spin bath during maintenance of the equipment, as is the case with the single spinnerets of a yarn spinning machine. Even more important, since the filaments issuing from the single set of spinnerets may total two million denier or more, it is entirely uneconomical to permit the viscose to continue to flow and be Wasted during the periods when tow is not being produced. If the sequence of steps presently to be described is followed, it becomes practical to mount the spinneret coupling more or less permanently in the trough or other container for thespin bath and at the same time to be able to shut off the flow of viscose and restart the flow whenever desired.

If the viscoseflow is shut off while the spinnerets are covered with the spin bath, some of the bath liquid will seep into the orifices of the spinnerets and cause the viscose within the orifices to set up and harden so that when subsequently the attempt is made to force the viscose through the spinnerets, many or all of the orifices will be clogged. Therefore, the first step in the method of stopping and restarting the machine is to withdraw the spin bath or coagulating liquid from the trough to a point where the surface of the liquid is below the faces of the spinnerets.

As soon as possible after the faces of all spinnerets are above the surface of the bath, the viscose supply to the spinnerets is shut off. Depending upon the angle of the spinneret faces to the horizontal, more or less of the viscose extruded after the removal of the bath and before the viscose flow is stopped will adhere to the outer faces of the spinnerets and since this will provide a thin layer or coating it will set up or harden rather quickly even at room temperature and unless removed the spinnerets with water, preferably cold water and preferably immediately after stopping the flow of viscose. The water may be applied under pressure and should be directed over not only the faces of the spinnerets but onto all exposed portions of the spinneret coupling and the outer cylindrical surfaces ,ofthe spinnerets so that no viscose is allowed to remain which may subsequently slough OE and contaminate the tow. Cold water is preferable because viscose can be hardened by heat alone and hot water would tend to cause the viscose within the spinnerets to solidify. I N

After the spinnerets and the coupling have been rinsed with water it will sometirnesbe found advisable to spray or otherwise coat the spinneret faces'with a material to reduce the surface tension of the water. :This is most advisable when the spinneret coupling is so mounted that the spinnerets face directly upward because the water is apt to form a film over some of the orifices and cling to the edges of the orifices" in a manneri which will interfere with the future flow of viscose. It has been found that Atlas Oil, a rosin-oil base material manufactured by National Rosin Oil Products, Inc. is suitable for this purpose but other surface tensionreducing agents are also satisfactory. The spinning station of the machine is now so conditioned that it may be permitted to remain idle for several hours.

In restarting the machine, the spin bath or coagulating liquid is introduced into the compartment in which the spinneret coupling is mounted until the desired depth of submersion is obtained and the flow of viscose is then resumed;

The above-described steps are shown in the accompanying drawing which is a flow sheet.

Having thus described the invention, what is claimed is:

1. In the wet spinning of viscose rayon filaments wherein viscose is extruded through a multiplicity of spinnerets fixed in a compartment containing a coagulating liquid the surface of which. normally covers the spinnerets, the method of stopping and restarting the spinning operation comprising the following steps in the order named: withdrawing coagulating liquid from the assasss compartment to a point where the surface of the liquid is below the faces of the spinnerets,stopping the flow .of viscose through the-spinnerets, rinsing the faces of the spinnerets, introducing coagulating liquid into the compartment to submerge the spinnerets, and resuming the flow of viscose through the spinnerets.

2. In the wet spinning of viscose rayon filaments wherein viscose is extruded through a multiplicity of spinnerets fixed in a compartment containing a coagulating liquid the surface of which normally covers the spinnerets, the method of stopping and restarting the spinning operation comprising the following steps in the order named: withdrawing coagulating liquid from the compartment to a point where the surface of the liquid is below the faces of the spinnerets, stopping the flow of viscose through the spinnerets, rinsing the faces of the spinnerets with cold water, introducing coagulating liquid into the compartment to submerge the spinnerets, and resuming theflow of viscose through the spinnerets.

3. In the wet spinning of viscose rayon filaments wherein viscose is extruded through a multiplicity of spinnerets fixed in a compartment containing a coagu lating liquid the surface of which normally covers the spinnerets, the method of stopping and restarting the spinning operation comprising the following steps in the order named: withdrawing coagulating liquid from the compartment to a point where the surface of the liquid is below the faces of the spinnerets, stopping the flow of viscose through the spinnerets, rinsing the faces of the spinnerets with cold water, coating the faces of the spinnerets with a surface tension reducing oil, introducing coagulating liquid into the compartment to submerge the spinnerets, and resuming the flow of viscose through the spinnerets.

References Cited in the file of this patent UNITED STATES PATENTS 1,818,549 Furmon Aug. 11, 1931 2,492,451 Wicker Dec. 27, 1949 2,536,093 Coleman Jan. 2, 1951 2,879,542 Haley Mar. 31, 1959 

1. IN THE WET SPINNING OF VISCOSE RAYON FILAMENTS WHEREIN VISCOSE IS EXTRUDED THROUGH A MULTIPLICITY OF SPINNERETS FIXED IN A COMPARTMENT CONTAINING A COAGULATING LIQUID THE SURFACE OF WHICH NORMALLY COVERS THE SPINNERETS, THE METHOD OF STOPPING AND RESTARTING THE SPINNING OPERATION COMPRISING THE FOLLOWING STEPS IN THE ORDER NAMED: WITHDRAWING COAGULATING LIQUID FROM THE COMPARTMENT TO A POINT WHERE THE SURFACE OF THE LIQUID IS BELOW THE FACES OF THE SPINNERETS, STOPPING THE FLOW OF VISCOSE THROUGH THE SPINNERETS, RISING THE FACES OF THE SPINNERETS, INTRODUCING COAGULATING LIQUID INTO THE COMPARTMENT TO SUBMERGE THE SPINNERETS, AND RESUMING THE FLOW OF VISCOSE THROUGH THE SPINNERETS. 